Last millennium northern hemisphere summer temperatures from tree rings: Part I: The long term context

Rob Wilson*, Kevin Anchukaitis, Keith R. Briffa, Ulf Büntgen, Edward Cook, Rosanne D'Arrigo, Nicole Davi, Jan Esper, Dave Frank, Björn Gunnarson, Gabi Hegerl, Samuli Helama, Stefan Klesse, Paul J. Krusic, Hans W. Linderholm, Vladimir Myglan, Timothy J. Osborn, Miloš Rydval, Lea Schneider, Andrew SchurerGreg Wiles, Peng Zhang, Eduardo Zorita

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Large-scale millennial length Northern Hemisphere (NH) temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed. This paper, and its companion (Part II, Anchukaitis et al. in prep), details the latest tree-ring (TR) based NH land air temperature reconstruction from a temporal and spatial perspective. This work is the first product of a consortium called N-TREND (Northern Hemisphere Tree-Ring Network Development) which brings together dendroclimatologists to identify a collective strategy for improving large-scale summer temperature reconstructions. The new reconstruction, N-TREND2015, utilises 54 records, a significant expansion compared with previous TR studies, and yields an improved reconstruction with stronger statistical calibration metrics. N-TREND2015 is relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time-scales from 918 to 2004 where at least 3 TR records exist from each major continental mass. N-TREND2015 indicates a longer and warmer medieval period (~900-1170) than portrayed by previous TR NH reconstructions and by the CMIP5 model ensemble, but with better overall agreement between records for the last 600 years. Future dendroclimatic projects should focus on developing new long records from data-sparse regions such as North America and eastern Eurasia as well as ensuring the measurement of parameters related to latewood density to complement ring-width records which can improve local based calibration substantially.

Original languageEnglish
Pages (from-to)1-18
Number of pages18
JournalQuaternary Science Reviews
Volume134
DOIs
Publication statusPublished - 15 Feb 2016

Keywords

  • CMIP5 models
  • Last millennium
  • Northern hemisphere
  • Reconstruction
  • Summer temperatures
  • Tree-rings

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